The invention relates to a corona ignition device comprising a housing, an insulator surrounded by the housing, an inner conductor leading through the insulator to an ignition tip, and a coil connected to the inner conductor. Corona ignition devices generally of this type are known from DE 10 2010 055 570 B3, U.S.2011/0305998 A1 and EP 1 662 626 A1.
If coils are exposed to jolting motions or vibrations, as occur in ignition devices, there is the risk that turns of the winding on the coil former will move. Both the function of the coil and also the service life thereof may be impaired as a result.
In order to fix wire turns on the coil former, coil windings can be sealed with synthetic resin or a silicone material. Here, it is problematic that even tiny bubbles impair the quality of the coil. In addition, thermal expansions of the sealing material may lead to the formation of cracks or splits and may thus lower the dielectric strength. Thermal expansions of the sealing material are a problem in particular with coils that are exposed to considerable temperature changes, as occur for example with ignition devices of internal combustion engines.
A further possibility for fixing wire turns on a coil former lies in providing the coil with a coating film, for example by dipping or spraying, or in winding adhesive tape around the coil, once the wire has been wound onto the coil former. Electrical properties of the coil, in particular the quality thereof, may be impaired, however, as a result.
In order to avoid undesirable movements of the wire turns on the coil former, it is also known to provide the coil former with a thread-like channel and to position the wire in this channel. This approach is very complex, however, in terms of manufacture.
A further possibility for fastening wire turns on a coil former is to apply an adhesive layer to the coil former. A problem here is that the adhesive has to be applied very uniformly in a thin layer. If, specifically, the adhesive layer thickness is too great, the wire sinks in the adhesive layer and the electrical properties of the coil are impaired, for example similarly to when fixing with a coating film applied by dipping or by spraying.